Light emitting device and method of manufacturing the same

ABSTRACT

A light emitting device includes a substrate, a light source, and a covering member. The light source has an optical axis, a light source bottom portion and a light source upper portion opposite to the light source bottom portion in the optical axis. The light source is provided on the substrate at the light source bottom portion. The covering member has a bottom surface and a top portion opposite to the bottom surface in the optical axis and is provided on the substrate at the bottom surface to cover the light source. The covering member has a recess portion on the top portion above the light source and around the optical axis. The covering member tapers toward the bottom surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U. S. C. §119 toJapanese Patent Application No. 2015-050645, filed Mar. 13, 2015. Thecontents of this application are incorporated herein by reference intheir entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a light emitting device and a methodof manufacturing a light emitting device.

2. Discussion of the Background

International Publication No. WO2012/099145 describes a batwing shapedlight distribution characteristic which is achieved by devising a moldedshape of a light emitting device. The contents of InternationalPublication No. WO2012/099145 are incorporated herein by reference intheir entirety.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a light emittingdevice includes a substrate, a light source, and a covering member. Thelight source has an optical axis, a light source bottom portion and alight source upper portion opposite to the light source bottom portionin the optical axis. The light source is provided on the substrate atthe light source bottom portion. The covering member has a bottomsurface and a top portion opposite to the bottom surface in the opticalaxis and is provided on the substrate at the bottom surface to cover thelight source. The covering member has a recess portion on the topportion above the light source and around the optical axis. The coveringmember tapers toward the bottom surface.

According to another aspect of the present invention, a method ofmanufacturing a light emitting device includes providing a substrate onwhich a light source is disposed. Resin is ejected from a nozzle ontothe substrate substantially around the light source in a circular shapeor a rectangular shape. The resin is hardened to provide a coveringmember having a recess portion above the light source.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIGS. 1A and 1B are a schematic top view and a schematic cross-sectionalview illustrating a structure of a light emitting device according to afirst embodiment;

FIG. 2 is a schematic cross-sectional view illustrating a structure of alight emitting device according to a second embodiment;

FIGS. 3A and 3B are schematic cross-sectional views each illustrating astructure of a light emitting device according to a third embodiment;

FIG. 4 is a schematic cross-sectional view illustrating a structure of alight emitting device according to a fourth embodiment;

FIG. 5 is a schematic cross-sectional view illustrating a structure of alight emitting device according to a fifth embodiment;

FIG. 6 is a schematic cross-sectional view illustrating a structure of alight emitting device according to a sixth embodiment;

FIGS. 7A to 7F are schematic views each illustrating a method ofmanufacturing the light emitting device according to the firstembodiment; and

FIG. 8 is a schematic graph illustrating light distributioncharacteristic of a light emitting device according to an example.

DESCRIPTION OF THE EMBODIMENTS

The embodiments will now be described with reference to the accompanyingdrawings, wherein like reference numerals designate corresponding oridentical elements throughout the various drawings.

Hereinafter, embodiments of the present invention will be described withreference to the drawings. However, a light emitting device and a methodof manufacturing the same in the following description are only providedto embody a technical idea, and the present invention is not limited tothe following description unless otherwise specified. Furthermore,contents described in one embodiment and one example can be applied toanother embodiment and another example.

Furthermore, the same name or reference numeral represents the same orsimilar member, and a detailed description is omitted as appropriate.Furthermore, as for each component in the embodiments of the presentinvention, a plurality of components may be formed of the same member sothat one member serves as the plurality of components, or to thecontrary, a function of one member may be implemented with a pluralityof members.

First Embodiment

FIGS. 1A and 1B are a schematic top view and a schematic cross-sectionalview illustrating a structure of a light emitting device according tothe first embodiment. FIG. 1A is the schematic top view, and FIG. 1B isthe schematic cross-sectional view taken along line I-I in FIG. 1A.

As illustrated in FIGS. 1A and 1B, a light emitting device 100 includesa substrate 120, a light emitting element 105 provided on the substrate120, and a covering member 108 for covering the light emitting element105. The covering member 108 has a recess portion 122 immediately abovethe light emitting element 105, and has a projection portion 124 aroundthe recess portion 122 in planar view. Here, a peak portion 111 servingas an uppermost portion of the projection portion 124 is formed into asubstantially circular shape in top view.

The covering member 108 is formed such that a width B of a bottomsurface is smaller than a maximum width A of the covering member 108.Here, the bottom surface means a connection surface of the coveringmember 108 with the substrate 120. In other words, a cross-sectionaldiameter of the connection surface of the covering member 108 with thesubstrate 120 is not a maximum cross-sectional diameter of the coveringmember 108. That is, the covering member 108 near the substrate 120 isformed into an inverted tapered shape. Thus, light emitted from thelight emitting element 105 in a direction perpendicular to an opticalaxis L can be refracted and directed to an upper side of the substrate,so that the light can be more externally extracted without hitting thesubstrate 120.

Substrate 120

The substrate 120 is a member on which the light emitting element 105 isset, and as illustrated in FIGS. 1A and 1B, includes an electricallyconductive wiring 102 for supplying power to the light emitting element105, and a base member 101 on which the electrically conductive wiring102 is disposed in an insulated manner

Examples of the material of the base member 101 include resin such asphenol resin, epoxy resin, polyimide resin, BT resin, polyphthalamide(PPA), or polyethylene terephthalate (PET), and ceramics. Among them,resin is preferably selected as an insulating material in view of lowcost and moldability. Alternatively, ceramics is preferably selected asthe material of the base member 101 in order to give high heatresistance and light resistance to the light emitting device. Theceramics includes alumina, mullite, forsterite, glass ceramics, nitrideseries (such as AlN), and carbide series (such as SiC). Among them,ceramics composed of alumina or ceramics containing alumina as a majorcomponent is preferably used.

In the case where the base member 101 is made of resin, glass fiber, oran inorganic filler of SiO₂, TiO₂, or Al₂O₃ may be mixed with the resin,to improve mechanical strength, to reduce thermal expansion rate, and toincrease light reflectivity. Furthermore, the substrate 120 may be ametal member having an insulating portion.

The electrically conductive wiring 102 is electrically connected to anelectrode of the light emitting element 105, and externally supply acurrent (power) thereto. In other words, the electrically conductivewiring 102 serves as an electrode or a part of the electrode forexternally applying the current. In general, at least two positive andnegative electrically conductive wirings are formed separately.

The electrically conductive wiring 102 is formed at least on an uppersurface serving as a mounting surface of the light emitting element 105in the substrate 120. The material of the electrically conductive wiring102 may be appropriately selected depending on the material of the basemember 101 and a manufacturing method. For example, in the case wherethe base member 101 is made of ceramics, the material of theelectrically conductive wiring 102 is preferably a high meltingtemperature material which can endure a firing temperature of a ceramicsheet, such as a high melting temperature metal like tungsten andmolybdenum. Furthermore, the surface of the electrically conductivewiring 102 may be covered with a metal material such as nickel, gold, orsilver by plating, sputtering, or vapor deposition.

Furthermore, when the base member 101 is made of resin, the electricallyconductive wiring 102 is preferably made of a readily processablematerial. Furthermore, when an injection molded resin is used for thematerial of the base member 101, the material of the electricallyconductive wiring 102 is preferably a readily processable material in apunching process, an etching process, and a bending process, and hasrelatively high mechanical strength. More specifically, the electricallyconductive wiring 102 may be a metal layer of copper, aluminum, gold,silver, tungsten, iron, nickel, iron-nickel alloy, phosphor bronze,copper-iron alloy, or molybdenum, or a lead frame. Furthermore, thesurface of the electrically conductive wiring 102 may be covered with ametal material. This metal material is not particularly limited, but maybe silver only, or a silver alloy with copper, gold, aluminum, orrhodium. In addition, the electrically conductive wiring 102 may be amultilayer film including the above silver and alloys. Furthermore, themetal material may be formed by a sputtering method or vapor depositionmethod other than a plating method.

Insulating Material 104

The substrate 120 may have the insulating material 104 as illustrated inFIG. 1B. The insulating material 104 preferably covers a region exceptfor a portion in which the electrically conductive wiring 102 iselectrically connected to the light emitting element 105 and anothermember. That is, as illustrated in FIG. 1B, a resist may be formed onthe substrate to cover and insulate the electrically conductive wiring102.

The insulating material 104 is formed to insulate the electricallyconductive wiring, but when it contains a white filler similar to anunderfill material which will be described below, the light can beprevented from leaking or being absorbed, so that light extractionefficiency can be improved in the light emitting device 100.

The insulating material 104 is not particularly limited as long as it isa material less likely to absorb the light from the light emittingelement and has an insulating property. Examples of the material includeepoxy, silicone, modified silicone, urethane resin, oxetane resin,acrylic, polycarbonate, and polyimide.

Light Emitting Element 105

The light emitting element 105 mounted on the substrate is notparticularly limited, and it can be a well-known element, but in thisembodiment, a light emitting diode is preferably used as the lightemitting element 105.

The light emitting element 105 may emit any wavelength. For example, ablue light emitting element or a green light emitting element may becomposed of ZnSe, nitride-based semiconductor (In_(x)Al_(y)Ga_(1-x-y)N,0≦x, 0≦y, x+y≦1), or GaP. Furthermore, a red light emitting element maybe composed of GaAlAs or AlInGaP. Furthermore, a semiconductor lightemitting element composed of another material may be used. Acomposition, an emitted light color, a size, and the number of lightemitting elements may be appropriately selected according to purposes.

In a case where the light emitting device includes a wavelengthconversion material, the nitride semiconductor (In_(x)Al_(y)Ga_(1-x-y)N,0≦x, 0≦y, x+y≦1) may be preferably used because it can emit light havinga short wavelength which can efficiently excite the wavelengthconversion material. The wavelength of the emitted light can bevariously provided by selecting a material of a semiconductor layer andits mixed crystal rate. Positive and negative electrodes may be formedon the same surface or on different surfaces.

The light emitting element 105 has a substrate for growth, and thesemiconductor layers stacked on the substrate for growth. Thesemiconductor layers include an n-type semiconductor layer, an activelayer, and a p-type semiconductor layer formed sequentially in thisorder. An n-type electrode is formed on the n-type semiconductor layer,and a p-type electrode is folined on the p-type semiconductor layer. Thesubstrate for growth may be a light-transmissive sapphire substrate.

As illustrated in FIG. 1B, the electrodes of the light emitting element105 are flip-chip bonded to the electrically conductive wiring 102formed on the surface of the substrate with a connection material 103interposed therebetween, and a surface opposite to the surface havingthe electrodes serves as a light extraction surface which is a principlesurface of the light-transmissive sapphire substrate. The light emittingelement 105 is disposed across the two negative and positiveelectrically conductive wirings 102, and bonded thereto with theelectrically conductive connection material 103. A mounting method ofthe light emitting element 105 may be, for example, a mounting methodusing a bump other than a mounting method using a solder paste.

Light Source

In this specification, the “light source” means a light emittingportion. Examples of the light source include the light emitting element105, the light emitting element 105 having a wavelength conversionmember, and a package incorporating the light emitting element (such asa light emitting device including a SMD, or a package type white LED),and its shape and structure are not particularly limited.

Connection Material 103

The connection material 103 is an electrically conductive member, andmore specifically, it includes Au alloy, Ag alloy, Pd alloy, In alloy,Pb—Pd alloy, Au—Ga alloy, Au—Sn alloy, Sn alloy, Sn—Cu alloy, Sn—Cu—Agalloy, Au—Ge alloy, Au—Si alloy, Al alloy, Cu—In alloy, and a mixture ofmetal and flux.

The connection material 103 may be in liquid form, paste form, or solidform (sheet form, block form, powder form, or wire form), and it can beappropriately selected according to a composition and a shape of asupport member. Furthermore, the connection material 103 may be a singlemember, or a combination of several kinds of members.

Underfill Material 106

As illustrated in FIG. 1B, the underfill material 106 is preferablyprovided between the light emitting element 105 and the substrate 120.The underfill material 106 contains a filler for the purpose ofefficiently reflecting the light from the light emitting element 105 andbringing its thermal expansion rate close to that of the light emittingelement 105.

The underfill material 106 is not particularly limited as long as it isless likely to absorb the light from the light emitting element. Forexample, the underfill material 106 includes epoxy, silicone, modifiedsilicone, urethane resin, oxetane resin, acrylic, polycarbonate, andpolyimide.

When the filler contained in the underfill material is a white filler,the light is more likely to be reflected, and the light extractionefficiency can be improved. Furthermore, as the filler, an inorganiccompound is preferably used. Here, the white filler includes a casewhere, even when the filler itself is transparent, it looks white due toscattering because of a difference in refractive index from a materialaround the filler.

Here, a reflectivity of the filler is preferably 50% or more withrespect to the wavelength of the emitted light, and more preferably 70%or more. In this case, the light extraction efficiency can be improvedin the light emitting device 100. A grain diameter of the filler ispreferably between 1 nm and 10 μm (inclusive). When the grain diameterof the filler falls within this range, the resin has a high fluidity asthe underfill material, and even a small space can be covered properly.Furthermore, the grain diameter of the filler is more preferably between100 nm and 5 μm (inclusive), and still more preferably between 200 nmand 2 μm (inclusive). In addition, a shape of the filler may be aspherical shape or scale-like shape.

More specifically, examples of the filler material include oxides suchas SiO₂, Al₂O₃, Al(OH)₃, MgCO₃, TiO₂, ZrO₂, ZnO, Nb₂O₅, MgO, Mg(OH)₂,SrO, In₂O₃, TaO₂, HfO, SeO, and Y₂O₃, nitrides such as SiN, AlN, andAlON, and fluorides such as MgF₂. These may be used alone or mixed.

In addition, a side surface of the light emitting element 105 is coveredwith the underfill material 106 in the example of FIG. 1B, but the sidesurface of the light emitting element 105 may not be covered with theunderfill material 106 by appropriately selecting and adjusting thegrain diameter of the filler and the underfill material. This is becausewhen the side surface of the light emitting element 105 is exposed fromthe underfill material 106, the side surface of the light emittingelement can serve as a light extraction surface.

Covering Member 108

The covering member 108 is formed on the substrate to cover the lightemitting element 105 in order to protect the light emitting element 105from an external environment, and to optically control the light emittedfrom the light emitting element 105.

As the material of the covering member 108, a light-transmissive resinsuch as epoxy resin, silicone resin, or mixed resin of those, and glassmay be used. Among them, the silicone resin is preferably selected inview of light resistance and moldability.

Furthermore, the covering member 108 may contain a wavelength conversionmaterial which absorbs the light from the light emitting element andemits light having a wavelength different from that of the light emittedfrom the light emitting element, and a light diffusing agent whichdiffuses the light from the light emitting element. Furthermore, thecovering member 108 may contain a coloring agent so as to correspond tothe light color of the light emitting element. Furthermore, since thecovering member 108 serves to control a light distribution from thelight source, it is preferable to limit content amounts of thewavelength conversion material, the diffusing material, and the coloringagent so that the covering member 108 can control the lightdistribution.

The covering member 108 may be formed by compression molding orinjection molding so as to cover the light emitting element 105. Otherthan that, as will be described below, the material of the coveringmember 108 may be dropped or drawn on the light emitting element 105after its viscosity is optimized, so that it can be formed into theshape illustrated in FIGS. 1A and 1B due to its surface extension.

Furthermore, the covering member preferably has a height in a directionof an optical axis smaller than a width. Thus, a brightness peakposition of a batwing light distribution can be provided on a widerangle side.

Method of Manufacturing Light Emitting Device

Hereinafter, a method of manufacturing the light emitting device 100will be described with reference to FIGS. 7A to 7F.

First, the substrate 120, on which the light emitting element 105 isdisposed, is prepared. Here, as one example, one light emitting device100 is illustrated, but a plurality of light emitting elements 105 maybe provided on one substrate, and one covering member 108 may be formedon each of the light emitting elements 105. Alternatively, the number ofthe light emitting elements 105 to be covered by one covering member 108is not limited to one, and the plurality of light emitting elements 105may be collectively covered with one covering member 108.

Subsequently, while the resin of the covering member 108 is ejected froma nozzle, the resin is applied onto the substrate 120 and the lightemitting element 105, substantially around the light emitting element105 in a circular shape. FIG. 7A illustrates with an arrow the movementof the nozzle while the resin is applied. As illustrated in FIG. 7A, theapplication of the resin starts from the top of the light emittingelement 105 and goes around the light emitting element 105 circularly.In this case, it is preferred that a resin ejection amount is small atthe top of the light emitting element 105 (the application startposition), so that the resin application amount at the top is smallerthan the resin application amount in the region around the lightemitting element 105.

In addition, as illustrated in FIG. 7D, the resin may be applied so asto circularly surround the light emitting element 105, and the resin iswet and spread on the light emitting element 105, so that the lightemitting element 105 is covered with the resin of the covering member108.

In this way, the resin is applied while the nozzle is moved, and theresin is then hardened, so that the covering member 108 has the recessportion 122 immediately above the light emitting element 105, and hasthe projection portion 124 around the recess portion 122 in planar viewas illustrated in FIGS. 1A and 1B. Thus, the covering member 108 can beformed by a simple method without using a die. Furthermore, in order toadjust the viscosity of the material of the covering member 108 in thismethod, the above-described fluorescent material or diffusing agent maybe used other than adjusting the viscosity of the material itself.

FIG. 7B illustrates an example in which application of the sealing resinstarts from the outside of the light emitting element 105 and ends atthe top of the light emitting element 105. That is, the nozzle forapplying the resin is moved in a direction opposite to that in FIG. 7A.In this case, by reducing an application amount at the end position, therecess portion 122 can be formed as described above.

Furthermore, the resin is not necessarily applied in the circular shape,and it may be applied in a polygonal shape. For example, the resin maybe applied along the outer shape of the light emitting element in planarview, that is, as illustrated in FIG. 7C, it may be applied in arectangular shape along the shape of the rectangular light emittingelement.

Furthermore, by adjusting the viscosity of the resin to be applied toadjust a contact angle with the substrate 120, the covering member 108can be readily formed into the shape in which the width B of the bottomsurface is smaller than the maximum width A of the covering member 108as illustrated in FIG. 1B. Thus, the covering member 108 near thesubstrate 120 can be readily formed into the inverted-tapered shape, sothat the light emitting device is excellent in external light extractionefficiency. In addition, the covering member 108 may be formed into ashape in which the width of the bottom surface is the maximum width.

Furthermore, in the case where the underfill material is formed asillustrated in FIG. 1B, after the light emitting element 105 is set onthe substrate 120, the resin of the underfill material is ejected from anozzle around an outer periphery of the light emitting element 105 in acircular or rectangular shape. Thereafter, it is left for a certaintime, and the underfill material moves and flows into a space betweenthe light emitting element 105 and the substrate 120. Then, theunderfill material is heated and hardened in this state and completed.

According to the light emitting device of this embodiment, the batwinglight distribution can be realized, so that even when the adjacent lightsources are apart from each other by 20 mm or more, brightnessunevenness is reduced in the light emitting device.

Second Embodiment

As illustrated in FIG. 2, a light emitting device 200 according to thesecond embodiment differs from the light emitting device 100 accordingto the first embodiment in that a light source 130 includes a lightemitting element 105 and a wavelength conversion member 109 covering thelight emitting element 105. In other portions, similar members to thosein the light emitting device 100 according to the first embodiment areused and configured similarly.

The wavelength conversion member 109 is formed so as to cover an uppersurface of the light emitting element 105. A side surface of the lightemitting element 105 is covered with an underfill material 106, so thatthe wavelength conversion member 109 is not directly in contact with theside surface of the light emitting element 105 in FIG. 2, but the sidesurface of the light emitting element 105 may be directly covered withthe wavelength conversion member 109.

Wavelength Conversion Member 109

The wavelength conversion member 109 absorbs the light from the lightemitting element 105 and converts a wavelength of the light to adifferent wavelength of light.

Examples of the wavelength conversion member 109 includeyttrium-aluminum-garnet (YAG)-based fluorescent material which isactivated with cerium, lutetium-aluminum-garnet (LAG)-based fluorescentmaterial which is activated with cerium, nitrogen-containing calciumaluminosilicate (CaO—Al₂O₃—SiO₂)-based fluorescent material which isactivated with europium and/or chrome, silicate ((Sr, Ba)₂SiO₄)-basedfluorescent material which is activated with europium, β-sialonfluorescent material, nitride-based fluorescent material such asCASN-based or SCASN-based fluorescent material, KSF (K₂SiF₆:Mn)-basedfluorescent material, and sulfide-based fluorescent material.Furthermore, other than the above florescent material, the fluorescentmaterial having the same function, action, and effect may be also used.

In addition, the wavelength conversion member 109 may be a lightemitting material called nanocrystal or a quantum dot. This material maybe a semiconductor material such as group II-VI, group III-V, or groupIV-VI semiconductors. More specifically, examples of the materialinclude nanosized high-dispersion particles of CdSe, core-shellCdS_(x)Se_(1-x)/ZnS, or GaP.

A height of the wavelength conversion member 109 in a direction of anoptical axis L is preferably ⅘ or less of a maximum width of a coveringmember 108. Thus, a lens effect of the covering member 108 can bemaintained.

Method of Manufacturing Light Emitting Device 200

The light emitting device 200 can be formed similarly to the lightemitting device 100 except that only the light emitting element 105serves as the light source in the light emitting device 100, while thelight emitting element 105 and the wavelength conversion member 109serve as the light source in the light emitting device 200.

The wavelength conversion member 109 may be formed into a convex shapeby potting a light-transmissive resin containing a fluorescent materialand a quantum dot, or may be formed by a printing method orelectrophoresis method. In addition, the wavelength conversion membermay be molded into a sheet shape and attached on the light emittingelement.

The same effect as in the light emitting device 100 can be obtained inthe light emitting device 200.

Furthermore, according to the light emitting device 200, the wavelengthconversion member 109 is formed around the light emitting element 105and serves as the light source 130, and the light source 130 is coveredwith the covering member 108 which practically does not contain thewavelength conversion member 109. Thus, compared with the case where theentire covering member 108 converts the wavelength, the batwing lightdistribution characteristic can be readily controlled.

Third Embodiment

As illustrated in FIG. 3A, according to a light emitting device 300 ofthe third embodiment, a small package-type white LED 201 is used as alight source, and except for that, the third embodiment is similar tothe first embodiment. Therefore, the light emitting device 300 achievesan effect similar to that in the first embodiment. The package-typewhite LED 201 is electrically connected to a substrate 120 with aconnection material 103 interposed therebetween. Due to thisconfiguration, a white color can be previously selected as the lightsource, so that a product yield concerning chromaticity can be improved.

Package-Type White LED

As for the package-type white LED 201, a light emitting element 105 anda wavelength conversion member 109 are housed in a package, and anexternal connection terminal is provided therein.

In particular, the package-type white LED 201 is preferably a CSP typebecause its size is close to the housed light emitting element.Furthermore, in order to enhance light extraction efficiency, a lightreflecting member is preferably provided therein.

For example, the package-type white LED 201 illustrated in FIG. 3B has alight reflecting member 126 formed on a side surface and a lower surfaceof the light emitting element 105, and an external connection terminal204 is exposed at the lower surface. Furthermore, a wavelengthconversion member 109 is formed so as to cover upper surfaces of thelight emitting element 105 and the light reflecting member 126. Asillustrated in FIG. 3A, an underfill material 106 is provided in a spacebetween the package-type white LED 201 and the substrate 120.

Fourth Embodiment

As illustrated in FIG. 4, a light emitting device 400 according to thefourth embodiment differs from the second embodiment in that a surfaceof a light source 130 formed of a light emitting element 105 and awavelength conversion member 109 is partially exposed from a coveringmember 108. That is, the covering member 108 has a through hole 140through which the light source 130 is exposed, and has a projectionportion outside the through hole 140 in planar view. An outer peripheryof the wavelength conversion member 109 is covered with the coveringmember 108. In other portions, similar members to those in the lightemitting device 200 according to the second embodiment are used andconfigured similarly.

The covering member 108 is preferably formed into a circular shape intop view, but it may be cut halfway such as a shape of C in top view,for example.

A method of forming the covering member 108 of the light emitting device400 may be similar to that of the light emitting device 100 according tothe first embodiment except that resin is to be applied around the lightsource 130 circularly so that the resin is not applied to a part of anupper surface of the light source 130 around an optical axis L, but theresin is applied to the outer periphery of the wavelength conversionmember 109 (for example, as illustrated in FIG. 7D).

In addition, the resin may be applied into a shape of C (FIG. 7E) or ina shape of a broken circle (FIG. 7F), and hardened as it is.

In this case, as described in the above embodiment, the width of thebottom surface of the covering member 108 may be smaller than themaximum width of the covering member 108, or as illustrated in FIG. 4,the width of the bottom surface of the covering member 108 may be themaximum width of the covering member 108.

According to the light emitting device 400, compared with the lightemitting device 200 according to the second embodiment, light extractionefficiency can be enhanced on a wide light distribution angle side withrespect to the direction of the optical axis L of the light source 130.

Fifth Embodiment

As illustrated in FIG. 5, a light emitting device 500 according to thefifth embodiment is similar to the light emitting device 100 accordingto the first embodiment except that a light reflecting/diffusing region113 is formed on a covering member 108 above a light emitting element105 to reflect and/or diffuse the light, so that the similar effect canbe provided.

In this configuration, the light emitted along an optical axis L is bentin a horizontal direction, so that light intensity along the opticalaxis L can be reduced compared with the light emitting device 100according to the first embodiment.

More specifically, the light reflecting/diffusing region 113 forreflecting and/or diffusing the light may be made of material similar tothe underfill material 106, and may be formed by extrusion molding afterthe covering member 108 is hardened, or may be formed by disposing areflecting member made of thermoplastic resin on the covering member 108and then softening it in a following heat treatment.

Sixth Embodiment

As illustrated in FIG. 6, a light emitting device 600 according to thesixth embodiment is similar to the light emitting device 100 accordingto the first embodiment except that a covering member 108 includes abubble 112 on a light emitting element 105. In addition, in thisconfiguration, the covering member 108 does not necessarily have acircular peak portion, and a batwing light distribution can be realizedeven when the covering member 108 has a normal domed shape. In addition,a shape of the bubble 112 includes several shapes such as sphericalshape, teardrop shape, or pyramidal shape.

For example, as illustrated in FIG. 6, when the shape of the bubble 112is a square pyramidal shape having a bottom surface shape substantiallyequivalent to an upper surface shape of the light emitting element, thelight emitted along an optical axis L is totally reflected, refracted,or scattered at an interface of the bubble 112, so that light intensityto the optical axis L can be reduced.

The bubble 112 can be formed in the light emitting device 600 in such amanner that before the resin of the covering member 108 is applied, alight source is subjected to an oil repelling treatment, and then theresin of the covering member 108 is applied from above. In addition, thebubble 112 may be formed by applying a foaming agent to the light sourcebefore the resin is applied.

Example

Hereinafter, the example according to the present invention will bedescribed in detail. Furthermore, the present invention is not limitedto the following example as a matter of course.

FIGS. 1A and 1B are a schematic top view and a schematic cross-sectionalview of a light emitting device 100 according to this example. In thisexample, a light emitting element 105 is mounted on a base member 101 insuch a manner that it strides across a pair of positive and negativeelectrically conductive wirings 102 provided on the base member 101 witha connection material 103 therebetween. In addition, an insulatingmaterial 104 is formed in a region except for an electrical connectionregion.

Furthermore, an underfill material 106 having a light reflectingfunction is formed on a lower portion and a side surface of the lightemitting element 105, and a covering member 108 is formed on an upperportion thereof. The covering member 108 has a recess portion 122immediately above the light emitting element 105 serving as a lightsource, and a projection portion 124 is provided outside the recessportion 122. A top portion (peak portion 111) of the covering member 108has a ring-like shape (substantially donut-like shape) in top view.

In this example, the base member 101 is made of glass epoxy basematerial, the electrically conductive wiring 102 is made of Cu (35 μm),and the insulating material 104 is made of epoxy-based white solderresist. Furthermore, the light emitting element 105 is a nitride-basedblue LED having a square shape having one side of 600 μm and a thicknessof 150 μm. The underfill material 106 is made of silicone resincontaining 30 wt % of titanium oxide filler, and the covering member 108is made of silicone resin.

Furthermore, it is preferred that the covering member 108 in thisexample does not have a light diffusing property, but it contains aminimal amount of filler to provide a thixiotropic nature to thecovering member. Thus, the light emitting device formed as describedabove can achieve a light distribution characteristic as illustrated inFIG. 8.

In addition, FIG. 8 is a schematic graph illustrating three patterns ofa large diameter (3.3 mm), a middle diameter (3.0 mm), and a smalldiameter (2.8 mm) of the peak portions 111 of the covering members 108.It can be seen from this graph that as the diameter of the peak portion111 is increased, the light from the light emitting element 105 morewidely spreads. In this way, by controlling the diameter of the peakportion 111, an angle of a corner portion of the batwing lightdistribution can be controlled.

A light emitting device according to an embodiment includes a substrate,a light source provided on the substrate, and a covering member forcovering the light source, in which the covering member has a recessportion or a through hole immediately above the light source, and awidth of a bottom surface of the covering member is smaller than amaximum width of the covering member.

Furthermore, a method of manufacturing the light emitting deviceaccording to an embodiment includes the steps of preparing a substrateon which a light source is disposed, applying resin onto the substratesubstantially around the light source in a circular shape or arectangular shape while the resin is ejected from a nozzle, andhardening the resin to form a covering member including a recess portionor a through hole immediately above the light source.

According to the embodiment of the present invention, there is providedthe batwing type light emitting device having high light emissionefficiency. Furthermore, according to the method of manufacturing thelight emitting device, the light emitting device can be manufacturedwithout using a die, and achieve the batwing light distribution.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed is:
 1. A light emitting device comprising: a substrate; a light source having an optical axis, a light source bottom portion and a light source upper portion opposite to the light source bottom portion in the optical axis, the light source being provided on the substrate at the light source bottom portion; and a covering member having a bottom surface and a top portion opposite to the bottom surface in the optical axis and provided on the substrate at the bottom surface to cover the light source, the covering member having a recess portion on the top portion above the light source and around the optical axis, the covering member tapering toward the bottom surface.
 2. The light emitting device according to claim 1, wherein the light source comprises at least one light emitting element.
 3. The light emitting device according to claim 1, wherein the covering member has a height at the optical axis in a direction of the optical axis and a maximum width on a plane perpendicular to the optical axis viewed in the direction of the optical axis, the height being smaller than the maximum width.
 4. The light emitting device according to claim 1, wherein the light source comprises at least one light emitting element, and a wavelength conversion member covering the at least one light emitting element.
 5. The light emitting device according to claim 4, wherein a height of the wavelength conversion member in a direction of the optical axis is ⅘ or less of a maximum width of the covering member on a plane perpendicular to the optical axis viewed in the direction of the optical axis.
 6. The light emitting device according to claim 1, wherein the covering member includes a bubble above the light source.
 7. The light emitting device according to claim 1, wherein the covering member includes a region to reflect or diffuse light at an upper side of the light source.
 8. The light emitting device according to claim 1, wherein a plurality of the light sources are provided, each of the plurality of light sources comprising the covering member, the plurality of the light sources being disposed spaced apart from each other by 20 mm or more.
 9. The light emitting device according to claim 1, wherein the recess portion is a hole to reach the light source upper portion.
 10. The light emitting device according to claim 9, wherein the light source comprises a wavelength conversion member on the light source upper portion, the recess portion reaching the wavelength conversion member.
 11. The light emitting device according to claim 1, wherein the covering member has a bottom width on the bottom surface viewed in a direction of the optical axis, wherein the covering member has a maximum width on a plane perpendicular to the optical axis viewed in the direction of the optical axis, and wherein the bottom width is smaller than the maximum width.
 12. A method of manufacturing a light emitting device, the method comprising: providing a substrate on which a light source is disposed; ejecting resin from a nozzle onto the substrate substantially around the light source in a circular shape or a rectangular shape; and hardening the resin to provide a covering member having a recess portion above the light source.
 13. The method according to claim 12, wherein ejecting resin starts at the light source.
 14. The method according to claim 12, wherein the resin is ejected after the light source is subjected to an oil repelling process.
 15. The method according to claim 12, wherein the resin is ejected after a foaming agent is applied to the light source. 